Minification

Concatenation

Concatenating or combining Javascript and CSS files into fewer files reduces the number of HTTP requests which improves performance.

CSS Sprites

CSS Sprites enable web developers to combine multiple images in a single image and use CSS to reference the images. This can significantly reduce the number of HTTP requests which improves performance.

Caching

Set HTTP cache headers, e.g. cache-control, so web browsers don't revisit the website to see if there is newer content. If you set a long expires then you should version the files.

General

In general

Reduce the number of HTTP requests

Reduce the number of libraries

Only load what you need and only when you need it

Serve static content from Cookieless domain so cookies not needlessly sent with every HTTP request